Adriamycin resistance, heat resistance and radiation response in Chinese hamster fibroblasts.

We have investigated the effect of heat, radiation or Adriamycin (ADR) on Chinese hamster fibroblasts (HA-1), their heat resistant variants, and their ADR resistant variants. Heat or ADR resistance did not confer cross resistance to radiation. Cells resistant to heat did show cross resistance to ADR. Cells selected for ADR resistance were not cross resistant to heat and they did not exhibit drug potentiation by hyperthermia, characteristic of ADR sensitive cells. Cytofluorometric measurement showed decreased ADR uptake in both heat and ADR resistant cells. The possibility of cross resistance between heat and ADR should be considered when designing treatment protocols involving combined modality trials.